Life on Venus. Is it True?

Do you even understand what world and time we live now? All this freaking news, which at first seem like fairy tales. Microchips in the head, cars that drive themselves, artificial intelligence, etc. And now there is a possibility of life on another planet! To my surprise ‒ this time everything was done without Elon Musk, his companies, or NASA, but the news will be interesting all the same!

What really happened?

On Monday, September 14, a group of scientists led by Jane Greaves of Cardiff University published the results of observations of the gas shell of Venus in the Nature journal.

We learned a lot about Venus in the 20th century. It has finally become known what our space companion looks like: detailed maps of its surface have been created, panoramas of Venusian landscapes have been obtained. But, perhaps, the readers have questions: “Why was all this? Why did countries spend hundreds of millions of rubles or dollars? Just to get some photos from another planet? And this is the result of the whole program?”

To begin with, one should not forget that the main reason for the flights to Venus was still not so much pure science as the romance of the pioneers. Venus and Mars at the beginning of the 60s of the twentieth century were seen as new continents, where the discoverers had not yet sailed. And then it seemed that it was necessary to explore these planets just so that the pioneer colonizers of these planets would have as few problems as possible. And this opinion was prevalent both in the USSR and in the USA.

In 2017, astronomers, using the James Clark Maxwell ground-based telescope, searched for inert gases or molecules that could be of biological origin in the planet’s atmosphere, and, along with other compounds, they were able to find traces of phosphine ‒ a substance consisting only of phosphorus and hydrogen, PH₃. Phosphine is one of the potential biomarker substances ‒ that may indicate the presence of life on the planet.

Two years later, the researchers continued to study the atmosphere of Venus using a completely different instrument ‒ the ALMA radio telescope complex. Astronomers again managed to find traces of phosphine and this time to study its distribution in the atmosphere ‒ it turned out that the substance is found mainly in the equator, at an altitude of 53–61 kilometers above the planet’s surface.

Based on the strength of the signal, the team calculated that the phosphine content of Venus’s atmosphere is approximately 20 ppb. At first glance, it may seem that this is negligible the opposite is true. The fact is that in the harsh, ultra-acidic conditions of the Venusian atmosphere, the average lifetime of this molecule is only about 16 minutes, which means that constant and rather powerful sources of matter are needed to produce the observed amount of matter.

And yet, it is not worth rushing with the statement that Venus is an alien planet.

Where does phosphine come from?

Used as a chemical weapon during the First World War, today this poisonous gas with the smell of rotting fish is used, for example, in agriculture to protect against pests and to create semiconductor materials. It can be produced industrially by reacting white phosphorus with sodium or potassium hydroxide, and in laboratories, it is made from phosphorous acid.

However, for astrobiologists, a completely different way of synthesizing a substance is important ‒ it is known that phosphine is also produced by some types of anaerobic (that is, constantly living without oxygen) bacteria. Such microorganisms live in acidic environments, for example, in some rivers or swampy soils, are found in bird guano and the intestinal tracts of animals.

Previously, phosphine was found on other planets of the solar system ‒ in particular, in the gas envelope of Saturn and the turbulent atmosphere of Jupiter. However, its production without the participation of living organisms, as astrobiologists recently found out (many of them were included in the team of authors of the new article), requires a lot of energy. On gas giants, it is formed in deep layers of the atmosphere at high temperatures and pressures and rises due to convective processes.

The hard surfaces of rocky planets, which include the Earth and Venus, serve as a natural barrier for phosphine, which is born in the interior (for example, with mutual friction of tectonic plates). The oxygen contained in the atmosphere and even inside surface rocks quickly destroys this gas, therefore, on our planet, the existence of phosphine is today associated exclusively with the activities of humans and microorganisms. And the same, the authors believe, is true for other rocky planets.

So is there life on Venus?

In favor of the statement about the possibility of life, the fact is that scientists still do not know the possible nonbiological mechanisms of phosphine production on Venus. So bacteria is a perfectly reasonable explanation. Other possible natural sources of phosphine ‒ heavy phosphorus-containing minerals ‒ are unlikely to rise as high as they were found. The chemical reactions associated with lightning flashes do not produce enough gas. On Earth, phosphine can also be produced by volcanoes, but the “tonnage” of such synthesis is very small: if only they were responsible for the production of gas on Venus, the volcanic activity would have to be about 200 times higher than on Earth.

On the other hand, astronomers are also rather restrained in their claims that the detection of phosphine unambiguously indicates the presence of living organisms in the atmosphere of Venus. First, the observations of the British-American team will need to be repeated and confirmed by other researchers. Moreover, several additional observations and simulations will have to be carried out. As a marker of possible life, phosphine is still very poorly studied (the authors of the article rely in fact on the only one, and their work, published in early 2020), and, likely, much in the models predicting its behavior has not yet been taken into account.

For example, it is possible that gas could accumulate in the middle layers of Venus’ atmosphere, where clouds hide it from the damaging effects of sunlight (details of how deeply phosphine may be in the atmosphere remain to be seen). Also, it is quite possible that processes, which are still unknown to science, but completely “natural”, that is, do not imply the existence of life, are involved in the production of phosphine.

It is also important to say that phosphine is far from the only substance considered by biologists as a biomarker. Oxygen, ozone, water, methane, and carbon dioxide are considered to be much more studied and known. The detection of these substances in the atmosphere of a planet similar in mass and radius to the Earth can be a powerful argument in favor of the presence of life forms known to us. However, each of these biomarkers individually can have a completely simple, abiotic origin, and its detection does not guarantee the discovery of alien civilizations. The same is true for phosphine: to speak with confidence about the detection of life, a whole set of biomarkers is needed that fit into a predictable and mutually consistent “ensemble”.

But is life on Venus possible in theory? Maybe it’s time to fly there and check?

Venus is often called the twin sister of our planet due to the similarity in size and mass, but the conditions on it are radically different from those on Earth. It has a dense atmosphere, mainly composed of carbon dioxide, and its average temperature reaches 462 degrees Celsius ‒ it is the hottest planet in the solar system, ahead of even the closest to the Sun-Mercury in this parameter. Besides, Venus is covered with a dense layer of sulfur clouds, and the atmospheric pressure at its surface is almost 90 times higher than Earth’s. “Let the conditions on the surface of Venus make the hypothesis of the existence of life there improbable, its clouds ‒ a completely different story,” wrote Carl Sagan and Harold Morowitz in the journal Nature back in 1967.

Venus clouds are quite interesting from an astrobiological standpoint. In addition to sulfuric acid, it also contains (albeit in extremely small quantities) the main ingredients for the life forms we know: water and organic compounds. Sunlight hits these substances, and at the middle level of the cloud layer, the pressure and temperatures no longer differ from those on Earth as much as on the surface. Hypothetically, under such conditions, terrestrial extremophiles could exist on Venus ‒ bacteria and microorganisms that can live and reproduce at very high temperatures and pressures. On Earth, extremophiles are found on the ocean floor near geothermal springs, in arctic deserts, and even in acidic bodies of water such as Rio Tinto in Spain.

In the future, the team intends to verify the data they received using the SOFIA stratospheric infrared observatory, operating from a Boeing 747 in flight. Also, the upcoming James Webb Telescope and the upcoming DAVINCI + and Venera-D missions, which could be launched between 2029 and 2031, can help validate new data.

Moreover, albeit planned missions, new, hitherto unknown players may now appear in the study of life on Venus. Today, immediately after the publication of data on the discovery of phosphine in Nature, Russian businessman Yuri Milner, founder of the Breakthrough Initiatives fund, announced plans to explore Venus. The group that will carry out this project sponsored by the foundation will be led by Sarah Seeger, an American planetary scientist at the Massachusetts Institute of Technology, who is also part of the team of authors of the new article.

Since the process of publication of such works usually stretches for many months, and the plans of the Milner Foundation were announced immediately after its release, it can be assumed that the foundation has long known about the results obtained by scientists and assessed the prospects for a future mission. Commenting on the results of the work of astrobiologists, Yuri Milner did not hide his joy: “The discovery of life anywhere outside the Earth would be a truly significant event,” the Foundation’s press service quotes him. “And if there is a slim chance that it is right next door to us, on Venus, then exploring this possibility is an urgent priority for our civilization.”

In the wake of interest in Venus, the head of the Russian “Roscosmos” Dmitry Rogozin already managed to tell that Russia also plans to send its expedition to Venus, in addition to the “Venera-D” (which is being prepared in cooperation with the United States). No details about this project are known yet, but it is not very difficult to imagine what it could be. Astronomer Vladimir Surdin, a senior researcher at the P.K. Sternberg Institute of the Russian Academy of Sciences, said that the most logical step for everyone who wants to explore Venus today would be to turn to the developments of Soviet missions that had already explored the planet in the late 80s.

Past

Life on Venus is a really serious discovery, and more weighty arguments are needed for evidence than an analysis of counted pixels in several panoramas. However, perhaps the most interesting questions and discoveries concern not the present of Venus, but its past.

Yes, Venus is now a red-hot hell. Being closer to the Sun, Venus receives almost twice as much heat as the Earth, which is one of the reasons for both the high temperature on its surface and high pressure.

But let’s fast forward to the past. Our Sun is an ordinary star, and in its development, it went through all those changes through which other stars pass and these changes have already been studied quite well by us. In particular, at the moment the luminosity of the Sun is growing. In other words, there used to be a time when Venus received as much solar radiation as the Earth is receiving now. Accordingly, the conditions on its surface were very similar to those on Earth. There, perhaps, the oceans splashed, in which, most likely, there was life, dinosaurs walked on land, and lizards flew in the clouds. Then, with the increase in temperature, the oceans dried up, sedimentary rocks like limestone, after annealing, released CO2 into the atmosphere.

According to this version, even earthly life can be the heir to the Venusian one! Back in the early twentieth century, the Swedish scientist Svante Arrhenius calculated that bacterial spores are quite capable of flying from one planet to another under the pressure of sunlight. But this spread can only be away from the Sun. That is, spores would not have been able to fly from Earth to Venus, but the path from Venus to Earth is already quite possible.

The fact that earlier the neighboring planet had a completely different hydro and atmosphere is convincingly evidenced by many different factors. For example, its relief. There is practically no trace of an early meteorite bombardment on it ‒ the very trace that is visible on Mercury, the Moon, and even Mars. There are no such “scars” on Earth. Of course, they once existed, but the active geological life of our planet swept them away. Yes, there are meteorite craters on Venus, but, as already mentioned, they are all extremely young.

They likely appeared after the planet acquired a dense atmosphere and got rid of the biosphere with the hydrosphere. So it is interesting to study it if only to understand what awaits our planet in the future when the increased activity of the Sun will turn the Earth into a second Venus. And maybe there will be invented the method how to avoid all this?

Also, if life once was, its traces are still there. They are hidden in Venusian sediments under sedimentary rocks, but they must be there and, as the author hopes, are waiting for their scientists. Can they be detected now, by our methods? Again, chances are there. According to planetologist A. T. Bazilevsky, for this, you need to try to take a soil sample on tesserae, one of the most ancient formations on Venus. It is there that the Venera-D landing is planned.

Better yet, deliver at least a small fragment to Earth. Even a pinch of such a breed could close many cosmogonic questions. Interestingly, no earth station has yet landed in such an area. For some reasons, this happened by chance, because when the stations were created, the relief was presented very approximately.

However, let’s hope that in the twenty-first century all questions will be answered.